[asterisk-ss7] At what interval should FISUs be sent?

Kristian Nielsen knielsen at knielsen-hq.org
Fri Jul 3 01:14:21 CDT 2009

"Gustavo Marsico [Gmail]" <gustavomarsico at gmail.com> writes:

> It's talking about Japan:
> Note: In the ITU-T Japan variant, signaling link quality is checked by the
> continuous transmission of flag octets (8-bit bytes) rather than FISUs;
> FISUs are sent only at predefined timer intervals (e.g., once every 150
> milliseconds).
> If you live in Japan can make sense that, but in ITU world it's just like as
> Kristian's said.

Yes, I meant ITU SS7. Forgot about the multiple variants ...

Here is the relevant quote from ITU Q.703:

11.2.2 For the basic error control method, the priorities are:
Highest    1. Link status signal units.
           2. Message signal units which have not yet been acknowledged and for which a
               negative acknowledgement has been received.
           3. New message signal units.
           4. Fill-in signal units.
Lowest     5. Flags.

So fill-in signal units are sent unless some serious error prevents sending
anything but flags.

Don't know about any other variants of SS7.

 - Kristian.

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